Ebola virus disease is a severe acute viral disease; its typical characteristics and physical signs include acute onset, fever, extreme weakness, muscle pain, headache and sore throat, followed by vomiting, diarrhea, rash, impaired kidney and liver function, and in some cases, both internal and external bleeding. Laboratory findings include low white blood cells and platelet counts, and elevated liver enzymes. Blood and secretions of human would be contagious when they contain viruses. Incubation period can persist 2-21 days.
This disease can affect humans and non-human primates (monkey, gorilla and chimpanzee). The virus is transmitted to people from wild animals (possible natural hosts such as fruit bats, etc.) and spreads in the human population through human-to-human transmission. Wherein, said human-to-human transmission includes direct contact (through broken skin or mucous membranes) with the blood, secretions, organs or other body fluids of infected people, and indirect contact with the environment contaminated with these fluids.
According to the report of World Health Organization by April 2014, the fatality rate of EVD can reach up to 90%, and severely ill patients require intensive supportive treatment.
Those at higher risk of infection when epidemic situation occurs are: health workers; family members or others in close contact with infected people; mourners who have direct contact with the bodies of the deceased during burial ceremonies; and hunters who come into contact with dead animals found in the rainforest area and forest, and the like.
So far, Ebola virus disease infections can only be confirmed through laboratory testing. Samples from patients are of extreme biohazard risk; and testing can only be conducted under maximum biological containment condition (level 4 biosafety laboratory). Health care workers and laboratory workers in other world-wide areas also often face great risk when a major epidemic situation outbreaks regionally.
Ebola virus is mainly transmitted via pathways such as the blood, saliva, sweat and secretions of patients. Laboratory tests often show lymphocytopenia, severe thrombocytopenia and elevated transaminases (AST>ALT), and sometimes blood amylase also elevates. For diagnosis, ELISA can be used for detecting specific IgG antibodies (occurrence of IgM antibody indicates infection); ELISA is used to detect antigens in blood, serum or tissue homogenate; IFA is used to detect viral antigens in liver cells via monoclonal antibodies; or viruses are isolated via cell culture or inoculation to guinea pigs. Viruses can be sometimes observed in liver slices using electron microscope. Misjudgment is often caused by using IFA to detect antibodies, especially when conducting serological investigations of past infections.
Up till now there has been little research on Ebola virus, and there is no good method for preventing, detecting and treating this virus in the world-wide range. So far, in terms of therapy, there is no available specific therapeutic method or vaccine which has acquired scientific confirmations for neither humans nor animals.
Currently, there is an urgent need for a set of research system capable of studying and analyzing the pathogenicity and replication mechanisms of Ebola virus from the view of genomics, further understanding the pathogenic causes and mechanisms of Ebola virus, and designing detection methods and therapeutic methods specifically directed to Ebola virus according to the research results.
In terms of detection, diagnosis is mainly made in prior art through detecting the specific IgM and IgG antibodies against Ebola virus, however, the antibodies in the blood of patients can only occur several days after attack, thus the problem of window phase exists; the viruses have begun to replicate during the window phase and the patients are highly contagious while the antibodies are not completely generated yet, therefore, it is very susceptible to cause the problem of false negatives.
In summary, there is an urgent need in this field for developing a drug capable of effectively inhibiting the replication of Ebola virus or treating Ebola virus, and there is still an urgent need for developing a method capable of being used for accurately detecting Ebola virus.